I like the tubular tap setup...looks very clean. I have built several keezers over the years and through my own trial and error and reading, I have learned that if you are going to leave a gap between the freezer wall and your paneling...you need to use fans of some sort. The best solution I have found is to adhere the panels directly to the freezer and make a cutout (or drill multiple holes) over the vent (usually on the side of the freezer) and cover with a decorative vent cover.

...as long as the side panels are warm to the touch, that means that it is displacing heat efficiently

The cabinet is essentially a 1x4 frame held together with pocket screws. Plywood on the back and the individual panels are just MDF that is glued and tacked with brads onto the plywood. I made a quick jig to hold the panels on edge and then ran them threw the table saw on their edges to cut the chamfer. Maybe 15 degrees or so I think. Basically I faked a rised panel, painted them black, scuffed the edges and then varnished the whole thing to protect the bare edges. You can see the plywood if you look at the end view where it's open. It's all screwed to the 2x4s that are on the base and that's glued to the freezer. Screw holes plugged and sanded flush.

I'm building another one for around my fish tank support but it will be free standing so I can move it to clean the filters.

The cabinet is essentially a 1x4 frame held together with pocket screws. Plywood on the back and the individual panels are just MDF that is glued and tacked with brads onto the plywood. I made a quick jig to hold the panels on edge and then ran them threw the table saw on their edges to cut the chamfer. Maybe 15 degrees or so I think.

That's pretty clever. Did you not have any issue with cutting the chamfer into MDF? I'd expect the fibers to have a significantly different texture than the top finish.